1. Field of the Invention
The present invention relates to an inkjet recording apparatus having a recording head including an ink-ejecting nozzle (an ejecting opening) and a cap for the recording head covering the recording head.
2. Description of the Related Art
In general, in an inkjet recording apparatus, a foreign material such as paper dust and dirt may be stuck to a nozzle of a recording head, or ink within the nozzle may be dried to increase in viscosity or to adhere to the nozzle, so that the nozzle may be clogged so as to have imperfect ejection (including non-ejection). Then, in order to prevent such clogging, a recovery mechanism has been used, in which in a non-recording mode, the nozzle is covered with a cap tightly while ink is sucked from the nozzle via the cap by sucking means such as a pump, so that the nozzle is normalized.
In an inkjet recording apparatus for recording by reciprocating a recording head mounted on a carriage, it is required to increase the capacity of an ink tank in order to reduce the replacement frequency of the ink tank. By the way, in an inkjet recording apparatus having a recording head formed integrally with an ink tank, when the capacity of the ink tank is increased, there is a problem that the inertia force of the recording head and the ink tank moving with the carriage is increased so that vibration and noise due to reciprocation scanning are liable to be produced. Therefore, an inkjet recording apparatus employing a so-called tube-feed system is also known, in which an ink tank (main tank) is fixed at a predetermined position in an apparatus body, and a sub-tank moving with the recording head on the carriage is connected to the main tank with a tube, etc.
In the inkjet recording apparatus, it is usually the case that in an other than recording mode, a very small negative pressure relative to atmospheric pressure is always applied thereto so as not to drop recording ink. This is for preventing unnecessary ink dropping in the non-recording mode, whereas in the inkjet recording apparatus employing the tube-feed system, along with drifting of the recording ink within the connecting tube due to the reciprocation scanning of the carriage, the ink within the sub-tank may be pushed out or drawn back so that the discharge amount fluctuates, resulting in recording unevenness or non-ejection.
As a measure to meet this problem, a technique employing an air-cushion container is known, in which an air reservoir is arranged in the vicinity of the recording head between the tube and the recording head so as to buffer pressure fluctuation due to ink drifting within the tube utilizing elasticity of air for stabilizing the ink discharge amount. The air-cushion container also serves to isolate air from the ink in the tube having air mixed therewith so as to supply only ink to the recording head by arranging an upper part of the container for the air reservoir and a lower part for an ink reservoir.
According to this configuration, a necessary liquid level of the ink reservoir needs to be maintained so as not to mix air from the air reservoir into the recording head. In order to prevent to mix air into the recording head, there is a system, in which recording is performed by transferring a recording medium without scanning the carriage; however, a similar container may be necessary for separating mixed air also in this case, so that the necessary liquid level of the ink reservoir formed inside needs to be maintained. The liquid level of the ink reservoir tends to decrease gradually due to permeation of air through a tube wall thereinto and deaeration of dissolved air in ink, so that means for maintaining the necessary liquid level is required.
In an inkjet recording apparatus, in which ink is supplied to the sub-tank from the main tank with one ink-feeding tube, a method for maintaining the necessary liquid level is proposed and performed, in which opening-and-closing means is arranged in an ink-passage while using sucking means of a recovery mechanism for the recording head. That is, in this system, after shutting off between the main tank and the sub-tank by closing the opening-and-closing means, ink in the recording head is sucked by the sucking means so as to generate a negative pressure in the recording head for controlling a vacuum in the air-cushion container. Then, the main tank is communicated with the sub-tank by opening the opening-and-closing means so as to restore the necessary liquid level.
However, in the inkjet recording apparatus described above, since when the interior of the air-cushion container is reduced in pressure, a large negative pressure is generated due to a cap, a cap rib is excessively deformed due to an elastic member so as to come closely in contact with the recording head, so that sealing of the recording head may be damaged so as not to obtain a sufficient vacuum.
Also, in a color printer using multicolor ink, discharge openings of the recording head may come in contact with an ink absorber within the cap of the recording head so that color ink of the recording head of each color is mixed with the other so as to generate a color mixture, resulting in extremely damaged recording quality.
It is an object of the present invention to provide a cap for a recording head capable of covering a nozzle of the recording head in a securely enclosed state during sucking of ink by a recovery mechanism, and to provide an inkjet recording apparatus using the cap for the recording head.
In accordance with a first aspect of the present invention, an inkjet recording apparatus comprises a recording head including a nozzle for ejecting ink formed on a nozzle-forming surface opposing a recording medium, and a cap for the recording head, which can be brought into and out of contact with the nozzle-forming surface and which covers the nozzle when abutting against the nozzle-forming surface. Further the cap for the recording head comprises an elastically deformable contact section for forming an enclosed space for covering the nozzle by being pressed into contact with the nozzle-forming surface, and an abutting section for abutting against the nozzle-forming surface of the recording head so as to restrict the amount of deformation of the contact section when the contact section is elastically deformed to have a predetermined amount of deformation by being pressed into contact with the nozzle-forming surface. Furthermore, the contact section and the abutting section are formed of a same member.
In accordance with a second aspect of the present invention, a cap for a recording head, which can be brought into and out of contact with a nozzle-forming surface arranged in an inkjet recording apparatus and which covers a nozzle when abutting against the nozzle-forming surface, the cap comprises an elastically deformable contact section for forming an enclosed space for covering the nozzle by being pressed into contact with the nozzle-forming surface, and an abutting section for abutting against the nozzle-forming surface of the recording head so as to restrict the amount of deformation of the contact section when the contact section is pressed into contact with the nozzle-forming surface to elastically deform to have a predetermined amount of deformation.
According to the present invention, when the nozzle-forming surface of the recording head is pressed in contact with the contact section under comparatively high pressure so that the contact section deforms to have a predetermined amount of deformation, the abutting section abuts against the nozzle-forming surface at that time so as to restrict the deformation of the contact section. Therefore, the contact section cannot deform excessively, enabling to properly maintain the close contact state to the nozzle-forming surface of the recording head and preventing ink from being dried and increased in viscosity. Also, even when a large negative pressure is generated within the cap during sucking of ink, excessive deformation of the contact section can be prevented by the abutment between the abutting section and the recording head. Moreover, since the abutting section and the contact section are formed of the same member, a clearance between the both sections cannot be generated during elastic deformation different from the case of being formed of different members, so that high-accuracy sealing can be obtained. Therefore, proper sucking by the cap is enabled so that recovery of the nozzle of the recording head or adjustment of the liquid level of the ink reservoir can be securely performed, resulting in improving reliability of the inkjet recording apparatus. Also, excessive deformation of a cap rib can be prevented due to the abutment between a stopper and the recording head, so that an ink absorber within the cap can be prevented from coming in contact with a discharge opening, thereby preventing a color mixture even in a multicolor printer.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.